For decades researchers have been working to increase storage density and reduce storage cost of data storage devices such as magnetic hard drives, optical drives, and semiconductor random access memory. However, increasing the storage density is becoming increasingly difficult because conventional technologies appear to be approaching fundamental limits on storage density. For instance, data storage based on conventional magnetic recording is rapidly approaching fundamental physical limits such as the superparamagnetic limit, above which magnetic bits are not stable at room temperature.
Storage devices that do not face these fundamental limits are being researched. A first example includes multiple electron sources having electron emission surfaces that are proximate a phase-change storage medium. During write operations, the electron sources bombard the storage medium with relatively high current density electron beams. During read operations, the electron sources bombard the storage medium with relatively low current density electron beams.
A second example includes a contact probe and a storage medium. In one embodiment, the storage medium is formed from a substrate, a conductive layer on the substrate, and a dielectric layer on the conductive layer. The probe records data in the storage medium by forming holes in the dielectric layer. The holes expose the surface of the conductive layer. During read operations, the probe is scanned across the storage medium. When the tip of the probe encounters a hole, the tip falls into the hole, and a short occurs between the probe tip and conductive layer.
These devices are purported to offer high storage density. However, the first example must still overcome the challenge of fabricating electron emitters that provide uniform and sufficient current density at small beam size for the recording. The second example suffers from tip wear out, and its recording speed is limited by the mechanical response time of the tip assembly.